1. Field of the Invention
The present invention relates to an infrared irradiation lamp for an automobile which is mounted on an automobile and illuminates a forward portion of a vehicle with an infrared light, and more particularly to an infrared irradiation lamp for an automobile which is to be shared with a CCD camera having a sensitivity up to a near-infrared.
2. Description of the Related Art
For example, this kind of lamp has such a structure that a visible light source and a reflector are provided in a lamp housing formed by a lamp body and a front lens, an infrared transmission globe having a surface coated with an infrared transmission multilayer film is provided to cover the visible light source, and an infrared light in a light of a light source which is transmitted through a globe is reflected by the reflector, is transmitted through the front lens and is distributed forwardly.
An image of infrared light irradiation region in a forward portion of a vehicle is captured by a CCD camera having a sensitivity up to a near-infrared which is provided in a front part of an automobile, is processed by an image processing apparatus and is projected onto a monitor screen in a vehicle compartment. A driver can confirm a person, a lane mark and an obstacle over the monitor screen projecting a field of view in the forward part of the vehicle at a great distance.
In the conventional infrared irradiation lamp, however, an infrared light transmission multilayer film cannot completely cut a visible light at the long-wavelength side of approximately 700 to 800 nm. Therefore, the lamp looks to be turned on. For this reason, there is a possibility such that the infrared irradiation lamp provided in the front part of an automobile might be erroneously recognized as a tail lamp or a stop lamp. Therefore, there is a problem in respect of its safety.
The inventor made investigations, and as a result, the red light component of the visible light which cannot completely be cut by the infrared light transmission globe (the visible light transmitted through the infrared light transmission globe) is guided to the whole reflector and a light reflected in a peripheral region of a light source in the reflector and emitted from the vicinity of the central part of a front lens has the highest energy (luminous flux density). Therefore, it has been confirmed that the vicinity of the central part of the front lens (the peripheral region of the light source in the reflector) is seen to emit a red light to be ring-shaped.
Therefore, the inventor supposed that the red light component of the visible light to be the cause of the lamp to be seen red is preferably diluted. Consequently, a diffusion step for diffusing a light is provided in the peripheral region of the light source in the reflector and in the vicinity of the central part of the front lens. Consequently, it has been confirmed that the diffusion step is effective for reducing a tone of color for the red light emission of the lamp. Thus, the invention has been proposed.
The invention has been made in consideration of the problems in the prior art and has an object to provide an infrared irradiation lamp in which the red light component of a visible light to be the cause for the lamp seen to emit a red light is diluted and is emitted from a front lens so that the lamp can be prevented from being erroneously recognized as a tail lamp or a stop lamp.
In order to achieve the object, a first aspect of the invention is directed to an infrared irradiation lamp for an automobile comprising a lamp housing formed by a lamp body and a front lens, a reflector provided in the lamp body, a light source provided ahead of the reflector in the lamp housing, and a cylindrical globe for infrared light formation which is provided to cover the light source and serves to shield a visible light and to transmit only an infrared light,
wherein a diffusion step is provided on a part of the reflector with being in a peripheral region of the light source, and/or a region on another part of the front lens with being corresponding to the peripheral region of the light source.
For first means, the diffusion step for diffusing and reflecting the red light component of the visible light transmitted and guided through the globe for infrared light formation is provided in the peripheral region of the light source of the reflector. For second means, the diffusion step for diffusing and transmitting the red light component of the visible light transmitted through the globe for infrared light formation and reflected and guided by the peripheral region of the light source in the reflector is provided in the region of the front lens corresponding to the peripheral region of the light source in the reflector. For third means, the diffusion step for diffusing and reflecting the red light component of the visible light transmitted and guided through the globe for infrared light formation is provided in the peripheral region of the light source in the reflector, and the diffusion step for diffusing and transmitting the red light component of the visible light diffused, reflected and guided by the peripheral region of the light source in the reflector is provided in the region of the front lens corresponding to the peripheral region of the light source in the reflector.
The diffusion steps to be provided in the reflector and the front lens include a fish-eye step and a cylindrical step.
The light distribution of the lamp includes the case in which a step for light distribution control is not provided on the front lens but the light is controlled and formed by only the reflector in addition to the case in which the light reflected by the reflector is controlled and formed at the step for light distribution control provided on the front lens. It is assumed that the front lens also includes the front lens having no step for light distribution control, that is, a so-called front cover.
As to the function performed by the first aspect of this invention, the red light component of the visible light which cannot completely be cut by the globe for infrared light formation (the visible light transmitted through the globe for infrared light formation) is reflected by the whole reflector and is emitted from the front lens. A light reflected by the peripheral region of the light source in the reflector and emitted from the vicinity of the central part of the front lens corresponding to the peripheral region of the light source has the highest energy (luminous flux density). For this reason, conventionally, the vicinity of the central part of the front lens (the region corresponding to the peripheral region of the light source in the reflector) is seen to emit a light like a red ring. In the invention, the red light component of the visible light transmitted through the globe for infrared light formation and guided to the peripheral region of the light source in the reflector is diffused by the diffusion step when it is to be reflected here (the peripheral region of the light source in the reflector), or the red light component is diffused by the diffusion step when it is to be reflected by the reflector and is to be then transmitted (emitted) through the front lens. Consequently, the luminous flux density of the red light component distributed forward from the vicinity of the central part of the front lens is reduced so that the red light emitted from the lamp is diluted.
Furthermore, the red light component of the visible light transmitted through the globe for infrared light formation and guided to the peripheral region of the light source in the reflector is diffused by the diffusion step when it is to be reflected by the reflector, and furthermore, is diffused by the diffusion step also when it is to be transmitted (emitted) through the front lens. More specifically, the red light component of the visible light reflected and diffused by the reflector is further diffused when it is to be transmitted through the front lens. Consequently, the luminous flux density of the red light component distributed forward from the vicinity of the central part of the front lens is more reduced than that in the case in which the diffusion step is provided in the reflector or the front lens so that the red light emitted from the lamp is diluted still more.
A second aspect of the invention is directed to the infrared irradiation lamp according to the first aspect of the invention, wherein the globe for infrared light formation has a rear end thereof provided apart from the reflector, and a light of the light source is directly guided from a clearance provided between the reflector and the rear end of the globe for infrared light formation to the peripheral region of the light source in the reflector.
As to the function performed by the second aspect of this invention, the light of the light source is directly guided to the inside of the peripheral region of the light source in the reflector and the light (white light) of the light source thus reflected is also emitted from the vicinity of the central part of the front lens corresponding to the peripheral region of the light source. Consequently, the luminous flux density of the red light component distributed forward from the vicinity of the central part of the front lens is further reduced.
A third aspect of the invention is directed to the infrared irradiation lamp according to the first or second aspect of the invention, wherein a shielding shade for shielding the light of the light source emitted from an opening on a front end side of the globe is provided ahead of the globe for infrared light formation, and a reflecting surface for reflecting the light of the light source and for guiding the reflected light to the peripheral region of the light source in the reflector is provided on a back side of the shielding shade.
As to the function performed by the third aspect of this invention, the shielding shade shields the light of the light source which is emitted from the opening on the front end side of the globe for infrared light formation, thereby impeding the generation of a glare light. Moreover, the light (white light) of the light source reflected by the reflecting surface on the back side of the shielding shade is reflected in the peripheral region of the light source in the reflector and is emitted as a diffused light from the vicinity of the central part of the front lens so that the luminous flux density of the red light component diffused and distributed from the vicinity of the central part of the front lens is further reduced.